Ink jet printing systems produce images by printing patterns of dots on a print medium, such as a sheet of paper. The dots are formed by drops of ink contacting the print medium. Such systems typically include two main mechanisms for determining the location of dots on the print medium, namely, a halftone mechanism and a shingling mechanism. Such mechanisms may be implemented, for example, in software, firmware, hardware, or a combination thereof, and may reference one or more lookup tables.
Typically, between passes of a printhead over a print medium, e.g., a sheet of paper, during a printing operation, the print medium is advanced, i.e., indexed, in the sheet feed direction by some amount. However, indexing errors can occur during the feeding of the print medium. For example, although the desired sheet feed amount may be some fraction (1/N) of the height of the printhead between successive passes, typically the paper advances either a little more (overfeed) or a little less (underfeed) than requested.
The ratio of dot size versus print resolution also is an important property of a printing system with respect to robustness to typical errors, such as indexing errors. If the dot size and spacing of the drops are such that the there is little overlap between adjacent drops, the printing system will be sensitive to small placement errors.